1. Field of the Invention:
The present invention relates to an automobile remote-control system for remote-controlling a door and the like of an automobile.
2. Description of the Prior Art:
There has heretofore been employed an automobile remote-control system for effecting a locking-and-unlocking operation of a door of an automobile or its trunk room and a lighting-and-extinguishing operation of a room lamp thereof. This kind of remote-control system is arranged such that the operator carries a transmitter, while the automobile is loaded with a receiver. A carrier which is so frequency-modulated or amplitude-modulated in a modulating circuit as to correspond to a code is transmitted from the transmitter, and the thus transmitted carrier is received through the intermediary of an appropriate antenna by the receiver. Subsequently, an adequate actuator is operated in accordance with the code, thereby performing the remote-control operation.
The above-described prior art automobile remote-control system is, however, attended with problems wherein the appropriate antenna has to be prepared separately from another radio receiving antenna, which arrangement not only brings about uneconomicalness but also spoils the appearance because of a plurality of antennas being protruded from the body of automobile. In addition, there arises a problem in which a dangerous situation with respect to the outer circumference of the body of automobile is worsened. Since the carrier is transmitted after being modulated in accordance with the code, a carrier oscillating circuit for outputting the carrier is consecutively controlled in an operation-state during the transmission thereof, resulting in a problem in which a large amount of electric power is consumed and a life-span of a power source battery built in the transmitter resultingly becomes short. Furthermore, the transmitter requires the modulating circuit for modulating the carrier; and at the same time a configuration of the circuit becomes intricate, which is the very obstacle both against miniaturization of the transmitter and against reduction in weight thereof. It is uncertain to know when the carrier is transmitted from the transmitter; and the receiver which is on the stand-by remains in the operation-state for a long period of time, thereby cosuming a great deal of electric power of the car battery for supplying the operation voltage to the receiver.